1. Field of the Invention
This invention relates to an EL (Electroluminescence) plane display device, and more particularly to an EL display device wherein photo luminescence layers are formed in the interior of a ZnS/Mn fluorescent layer to display multiple colors.
2. Discussion of Related Art
As shown in FIG. 1, a conventional EL display device is constructed for displaying an image or form of information, by sputtering In.sub.2 O.sub.3 onto a glass substrate (1) to form transparent electrodes (2) having the shape of stripes formed in rows by photo etching techniques and then sequentially depositing a lower insulation layer (3) of Si.sub.3 N.sub.4, a fluorescent layer (4) of AnS/Mn and a upper insulation layer (5) of Si.sub.3 N.sub.4 thereon and, thereafter, forming rear aluminum electrodes (6) having the shape of stripes on the upper insulation layer (5) in rows in a direction perpendicular to that of the first transparent electrodes. An a.c. pulse voltage (7) is applied between the transparent electrodes (2) and rear electrodes (6).
The operational procedure of the EL display device constructed as described above will now be explained with reference to FIG. 3.
If an a.c. pulse voltage (7) is applied between the transparent electrodes (2) and the rear electrodes (6), then an electric field (E) is induced in the interior of the fluorescent layer (4) between the transparent electrodes (2) and the rear electrodes (6) opposed to each other, and thus electrons (e) existing between the boundary surfaces of the upper and lower insulation layers (5) and (3), and the fluorescent layer (4) are accelerated and emitted into the interior of the fluorescent layer (4) by the electric fields, to impact and excite Mn atom within the interior, so that the EL display device luminesces only a yellowish-orange color having a wavelength of 5850 angstroms inherent to Mn.
Therefore, the conventional EL display device has the drawback that it cannot display an image or information as various colors, but only as a monochromatic yellowish-orange color.